The present invention relates to an improved preservation solution for organs and tissues, or parts thereof, from humans and animals.
In coronary artery surgery (about 800 operations per one million inhabitants a year) and in peripheral vascular surgery (about 100 operations per one million inhabitants a year), so-called physiological saline solution (0.9% NaCl) is in use today in most European clinics as a solution for washing away blood from blood vessel transplants, and for storing blood vessel transplants before inserting them in their new positions. In coronary artery surgery, use is generally made of the vena sapena magna, i.e. the superficial vein extending from the inside of the foot over the inner ankle and along the inside of the lower leg and the thighbone to the groin, where it joins the thigh vein (vena femoralis). In a coronary artery operation, first the vena sapena magna in one leg is removed, while the breastbone is opened and preparatory measures are taken for connection to a heart-lung machine. After removal of the vena sapena magna, this blood vessel is flushed with saline solution of the above-mentioned type, on the one hand to wash away all blood from the inside of the vessel and, on the other hand, to ensure that one has not neglected to ligate any branch of the vein, i.e. to tie the branches with a thread with a view to preventing leakage therethrough. Subsequently, the removed vein is placed in a dish containing saline solution of room temperature, i.e. 20-25xc2x0 C. Then the heart-lung machine is connected and cardioplegia is given to the heart. About 15-20 cm-long segments are cut off from the vein in the dish and are sewn as a so-called aortacoronary vein bypass to the sick coronary arteries. Before all vessel transplants are sewn and the blood again circulates through these, a period of up to 2 hours may have passed. For patients who are to have one or two cardiac valves inserted as well, this period can be still longer.
Instead of storing the vessel transplants in saline solution before being sewn, some surgeons use the patient""s own blood. Blood is then drawn off from the patient and is placed in a dish. The transplant is then allowed to lie in this blood before being sewn to the heart. First the temperature is 37xc2x0 C. but rapidly falls to room temperature. It is thought that since blood is the medium to which the vessel is exposed throughout life, this would be the ideal storage medium for a vascular transplant.
In heart surgery, the coronary artery surgery constitutes about 70% of the operations on adults. It is well known from studying experiments on animals that when a vascular transplant is used where the endothelium is destructed, so-called intimal hyperplasia is released and the transplants are occluded after some time (the vascular lumen becomes smaller and smaller and at last the flow of blood is stopped completely). In clinical follow-up studies, it has been found that 5 years after a coronary artery operation about 30-50% of the venous transplants have been occluded, and when these are studied histologically, a pronounced intimal hyperplasia will be discovered. This thus applies to venous transplants which have been rinsed and stored in the above-mentioned physiological saline solution.
The applicant""s research team has intensely studied both short-term and long-term preservation of blood vessels. Regarding short-term preservation of blood vessels, i.e. up to 2 hours preservation, it has been found that a physiological saline solution is toxic to the vascular endothelium. If a saline solution is flushed through, for example, the arteria iliaca of a rat, intimal hyperplasia can be found in the vessel after about one month. If, on the other hand, serum is used for rinsing correspondingly, no intimal hyperplasia will be discovered. Thus, the use of a physiological saline solution as preservation solution is not favourable to the blood vessels. All the same and in the absence of a better alternative, the clinical use of physiological saline solution, however, continues in most thoracic surgery centres throughout the world.
The applicant""s research team has also demonstrated that blood is not satisfactory as a preservation solution. Blood of room temperature which is stored in a dish and is not oxygenated is extremely toxic to the endothelia of the blood vessels and inhibits the endothelial function to a considerable extent. This may seem to be a paradox, but since blood is an organ that has its normal function only when it is moving and is continuously oxygenated in the lungs, it cannot function in the normal manner. Deoxygenated, non-moving blood contains, like all other blood, white and red blood corpuscles and thrombocytes. Indeed, it is well known that white blood corpuscles are activated in case of hypoxaemia (low concentration of oxygen), and that they then produce toxic substances.
The applicant""s research team has also confirmed that extracellular solutions can preserve blood vessels, but only for limited times, at room temperature. Extracellular solutions, in the literature sometimes misleadingly called preservation solutions, are solutions having ionic concentrations similar to plasma. The classic extracellular solution is Ringer""s solution, which has a normal extracellular concentration of sodium, potassium, calcium and magnesium. To match the positive ions for obtaining ionic equivalence, chloride, lactate or acetate are used in different types of Ringer""s solution. For functional in vitro studies the classical organ bath solution is Krebs solution which is electrolytically constructed like Ringer""s solution. However, Krebs solution also contains glucose for metabolism, and it contains phosphate and bicarbonate buffers to achieve a pH of 7.40 when this solution is bubbled with a mixture of 95% oxygen and 5% CO2 at 37xc2x0 C. If a cold perfusion is preferred, enough oxygen is physically dissolved to match the lowered metabolism caused by the cooling. However, neither of these two methods have been a success for extended preservation periods in experimental transplantation. During the cooling of hypothermia, rigidity develops in the cell endothelial membranes. This occurs because the fluidity of the lipids is diminished as an effect of the temperature reduction. The rigidity of the endothelium contributes to the endothelial injury described following prolonged cold perfusion with the intention to preserve, for example, the kidney and the liver.
Extracellular solutions exhibit what has been called the xe2x80x9ccalcium paradox.xe2x80x9d If an organ is perfused with an extracellular solution without calcium for a while, and then the perfusion continues with the same solution but now including calcium, the organ may be destroyed more quickly compared to perfusing it only with the calcium free solution, i.e. perfusion without calcium is dangerous, and perfusion with calcium is dangerousxe2x80x94that is the paradox. In clinical organ preservation, the organ is immediately cooled down by flushing it with a cold preservation solution created, for example, for cold anaerobic storage.
It should be emphasized that the composition of preservation solutions used for cold anaerobic storage needs to be constructed in quite another way than conventional extracellular solutions. This is due in part, at least, to the effects of hypothermia.
In the first successful liver transplantation performed, Welch found that 33 minutes of warm ischemia of the dog liver was the upper limit, if the recipient animal was going to survive the operation (Goodrich E O, Welch H N, Nelson J A et al: Homotransplantation of the canine liver. Surgery 39:244, 1956. This reference is incorporated by reference herein.). With this approach, success was noted in 21 of the 49 cases, which survived for at least 5 days. Moore et al., were the first to describe the use of hypothermia in preservation of the liver, namely by surface cooling of the organ, but they did not attempt to prolong the ischemic time to more than half an hour (Moore F D, Smith L L, Bumap T K et al.: One stage homotransplantation of the liver following hepatectomy in dogs. Transplant Bull 6:103, 1959. This reference is incorporated by reference herein.). In addition to cooling the whole donor animal by immersing it in an ice bath, Starzl also used so-called core cooling of the liver by flushing out the blood through the portal vein with chilled Ringer""s lactate solution (Starzl T E, Bernhard V M, Cortes N, Benvenuto R: A technique for one-stage hepatectomy in dogs. Surgery 47:880, 1959; Starzl T E, Kaupp H A, Brock D R, Lazarus R E, Johnson, R F: Reconstructive problems in canine liver homotransplantations with special reference to the postoperative role of hepatic venous flow. Surg. Gyn Obstet 111:733, 1960. These references are incorporated by reference herein.). He thereby found that cold ischemic times for up to 2 hours were compatible with survival of the recipient dog, but longer ischemic times resulted in a so-called venous outflow block, leading to the death of the recipient.
It was apparent from these and subsequent studies that hypothermia had a protective effect during ischemia, and in fact, hypothermia has become the main principle in organ preservation. For example, Calne and Pegg showed that simple cooling of ischemic kidneys with cold blood was effective for preserving the function for 12 hours (Calne R Y, Pegg D E, Pryse-Davies J, Leigh-Brown F: Renal preservation by ice-cooling, An experimental study relating to kidney transplantation from cadavers. Br MedJ 2:651, 1963. This reference is incorporated by reference herein.). By investigating recipients of paired cadaver kidneys subjected to up to 1 hour of warm ischemia, followed by up to 10 hours of cold ischemia, Bergentz et al. showed that the function was immediate after transplantation of these kidneys (Bergentz S E, Brunius U, Claes G, Gelin L E, Lewis D H: Double cadaver renal transplantations: An analysis of twenty-one pairs with special reference to the effect of variations in ischemic time, Ann Surg 170:996, 1969. This reference is incorporated by reference herein.).
Hypothermia probably exerts its protective effect during ischemia by reducing the rate of cellular metabolism. The reduction in the activity of most enzymes in normothermic animals is approximately 12- to 13-fold when the temperature is reduced from 37xc2x0 C. to close to 0xc2x0 C. Most organs can tolerate a warm ischemic period for 30 to 60 minutes without loss of function. Thus, it could be predicted that simple cooling of the organ could prolong the tolerance of an organ to ischemia to 6-12 hours, which in the case of the kidney is in accordance with the findings of Calne and Pegg, and for the lungs with the findings of Steen (Steen S, Sjxc3x6berg T. Ingemanson R, Lindberg L: Efficacy of topical cooling in lung preservation. Is a reappraisal due?, Ann Thorac Surg 1994; 58:1657-63. This reference is incorporated by reference herein.). Thus, cell metabolism decreases during hypothermia, and the consumption of oxygen is reduced. For example, at 5xc2x0 C., the oxygen consumption in the kidney is known to be only about 5% of the value at normothermia.
Hypothermia per se has certain negative side effects resulting in the need for special preservation solutions for cold anaerobic storage. One side effect of hypothermia is an inhibition of the Na/K ATPase, causing a pronounced cell swelling during hypothermia. In fact, since the sodium pump becomes inoperative because of the cooling, swelling will occur even if sufficient ATP is present. The same degree of swelling that occurs in tissue slices incubated at 0xc2x0 C., can be provoked by incubation with ouabain, an inhibitor of Na/K ATPase (D""Allesandra A, Southard J H, Kalayglou M, Belzer F O: Comparison of cold storage and perfusion of dog livers on function of tissue slices. Cryobiology 23:161, 1986. This reference is incorporated by reference herein.). Hypothermia induced cell swelling is more prominent in the heart and liver than in the kidney, because of a difference in cold sensitivity of the membrane pumps between these tissues (Martin D R, Scott D F, Downes G L, Belzer F O: Primary cause of unsuccessful liver and heart preservation: cold sensitivity of the ATPase system. Ann Surg 175:11, 1972. This reference is incorporated by reference herein.). Similar to the situation during warm ischemia, there will be a cellular loss of potassium and a gain of sodium and calcium as an effect of the inhibition of the membrane pumps.
During normal resting conditions, the intracellular Ca2+ concentration is 1,000-10,000 times lower than that of the extracellular fluid (Kretsinger RH: The informational value of Ca2+ in the cytosol, Adv Cyclic Nucleotide Res 11:1, 1979. This reference is incorporated by reference herein.). This large gradient is maintained by the action of the Ca2+ sequestering system in the mitochondria and endoplasmic reticulum, as well as by the action of the Na/Ca ATPases of the endoplasmic reticulum and the cell membranes (Trump B F, Berezeky I K: Role of sodium and calcium regulation in toxic cell injury, In Mitchell J R, Horning M G, eds.: Drug metabolism and Drug toxicity, Raven Press, New York, 1984. This reference is incorporated by reference herein.). Thus, lack of ATP will lead to an increase in the cytoplasmic concentration of Ca2+. Based on the finding that Ca2+ accumulates in liver cells damaged by either ischemia or different hepatotoxins (Bergentz et al., id.; Trump et al. id.; Keppler D., Popper H, Bianchi L, Reutter W, eds: Mechanism of hepatocyte injury and death, MTP Press, Lancaster, England, 1984; Zimmerman H J: Hepatotxicity: The adverse effects of drugs and other chemicals on the liver, Appleton-Century-Crofts, New York, 1978; Farber J L: Calcium and the mechanisms of liver necroses, In, Popper H, Schafffner F, eds.: Progress in liver diseases, Vol. 7, Grune and Straton, New York, 1982, chap. 20. These references are incorporated by reference herein.), Farber has suggested that inflow of Ca2+ from the extracellular fluid is a final common pathway in liver cell death (Farber, id.; Schanne F A, Kane A B, Young E E, Farber J L: Calcium dependence of toxic cell death: a final common pathway, Science 206:700, 1979; Casini A F, Farber J L: Dependence on carbon tetrachloride-induced death of cultured hepatocytes on the extracellular calcium concentration. Am J Pathol 105:138, 1981; Farber J L: The role of calcium in liver cell death, In Keppler D, Popper H, Bianchi L, Reutter W, eds: Mechanism of hepatocyte injury and death, MPT Press, Lancaster, England, 1984. These references are incorporated by reference herein.). It has also been shown that blockers of Ca2+ entry will alleviate liver cell injury (Schanne F A, et al. id., McClean A E M, McLean E, Judah J D: Cellular necrosis in the liver induced and modified by drugs, Int Rev Exp Pathol 4:127, 1965; Landon E J, Jaiswal R K, Naukam R J, Sastry B V R: Effects of calcium channel blocking agents on membrane microviscosity and calcium in the liver of carbon tetrachloride treated rat, Biochem Pharmacol 33:3553, 1984; Fleckenstein A., Frey M, Fleckenstein-Grun G: Cellular injury by cytosolic calcium overload and its prevention by calcium antagonistsxe2x80x94a new principle of tissue protection, In Keppler D, Popper H, Bianchi L, Reutter W, eds: Mechanism of hepatocyte injury and death, MTP Press, Lancasterm England, 1984; Lefer A M, Papanicolaou G: Beneficial action on two novel calcium channel blockers in the isolated perfused hypotoxic cat liver, Methods Findings Exp Clin Pharmacol 7:59, 1985. These references are incorporated by reference herein.). Further, calcium ionophors, i.e., compounds that facilitate Ca2+ entry across cell membranes, have been shown to cause liver cell death (Lamb R G, Snyder J W, Coleman J B: New trends in the prevention of hepatocyte death, Modifiers of calcium movement and of membrane phospholipid metabolism, In Testa B, Perissoud D., eds.: Liver drugs: From experimental pharmacology to therapeutic application, CRC Press, Boca Raton, Fla., 1988, Chapter 4. These references are incorporated by reference herein.). As a result of these findings, organ and tissue preservation solutions created for cold anaerobic storage have always been constructed without Ca2+.
As earlier mentioned, Starzl used cold Ringer""s lactate solution, i.e. not a genuine preservation solution, to flush the liver to obtain core cooling quickly, and this allowed for 2 hours preservation in the dog liver transplantation model. Because of the relative inefficiency of this technique, however, research for several years focused on other methods for organ preservation.
However, in 1969 there was a breakthrough for preservation by simple cold storage. Collins showed that simple cold storage of the kidney for 30 hours was possible with a new type of hypertonic flushout solution, hereafter called Collins solution (Collins G M, Bravo-Shugarman M, Terasaki P I: Kidney preservation for transportation. Initial perfusion and 30 hours ice storage. Lancet 2:1219, 1969. This reference is incorporated by reference herein.). This solution came into immediate use for clinical kidney preservation, and soon became the most used solution worldwide. This solution was calcium free, and had intracellular concentrations of sodium and potassium, i.e. low sodium and high potassium concentrations.
In 1977, Collins solution was tried for preservation of the liver, and it allowed 18 hours of preservation of the canine liver (Benichou J, Halgrimson C G, Weil R III, Koep L J, Starzl T E: Canine and human liver preservation for 6 to 18 hours by cold infusion, Transplantation 24:407, 1977. This reference is incorporated by reference herein.). This solution was then adopted by Starzl""s group for clinical liver preservation (Beichou et al. id.; Starzl T E, Iwatsuki S, Esquivel C O et al.: Refinements in the surgical technique of liver transplantation, Sem Liv Dis 5:349, 1985. This reference is incorporated by reference herein.), and was slightly modified to what is called Euro-collins solution (Dreikorn K, Horsch R, Rohl R: 48- to 96-hour preservation of canine kidneys by initial perfusion and hypothermic storage using the Euro-Collins solution, Eur Urol 6:221, 1980. This reference is incorporated by reference herein.), and became the most extensively used liver and kidney preservation solution until the development of the University of Wisconsin preservation solution. Since the extracellular solution Ringer""s lactate allows only 2 hours and the intracellular solution Collins solution allows up to 18 hours of cold storage of the canine liver (Starzl T E, et al., Reconstructive problems . . ., id., and Levy, id.), it was obvious that the composition of the cold storage solution influences the results of preservation during cold anaerobic storage. Initially, most authors regarded the success behind Collins solution as a result of its high content of potassium (Collins G M, Hartley L C J, Clunie G J A: Kidney preservation for transportation. Experimental analysis of optimal perfusate composition. Br J Surg 59:187, 1972; Collins G M, Halasz N A: Forty-eight hour ice storage of kidneys: Importance of cation content. Surgery 79:432, 1976; Jensen E H: Preservation of rabbit kidneys without perfusion. The significance of the Na+/K+ ratio; the phosphate concentration and the dextrose concentration in the washout fluid. In Pegg D E, ed.: Organ preservation. Churchill Livingstone, Edinburgh and London, 1973, pp. 7-15. The cited portions of these references are incorporated by reference herein.). It was assumed that the intracellular composition of this solution was saving high energy phosphate by decreasing the load of the cell membrane pumps (Collins, Halasz, et al., id.). In the early studies it was also assumed that the high content of magnesium was important for the results obtained with Collins solution, presumably by preventing the loss of potassium (Collins, Hartley et al., id., and Collins Halasz et al., id.). For that reason, Collins solution had a high magnesium content.
However, the role of magnesium was later questioned by other authors, obtaining equally good or even better results with solutions with a low or no content of magnesium (Jensen, id.; Downes G, Hoffman R, Huang J, Belzer F O: Mechanism of action of washout solutions for kidney preservation. Transplantation 16:46, 1973; and Mieny C J, Myburgh J A, Smit J A: Liver preservation in the primate by simple cooling. In Lie T S, Gutgemann A, eds.: Liver Transplantation. Verlag Gerhard Witzstrock GmbH, Baden-Baden, 1974 pp. 145-148. The cited portions of these references are incorporated by reference herein.), and in a tissue slice model it was shown that the presence of Mg2+ did not influence the loss of K+ during hypothermia (Downes, et al., id.). For that reason, magnesium was taken away in the Euroxe2x80x94collins solution, which then was free from both calcium and magnesium. Then the attention was focused on the content of cell membrane impermeant solutes in Collins solution. Collins solution has a high content of glucose and sulfate, which are relatively impermeable in kidney cells. By balancing the osmotic pressure created by the intracellular cell membrane impermeable anions with cell membrane impermeable substances in the preservation solution, the development of hypothermia induced cell swelling during cold storage of the kidneys could be prevented.
Glucose is relatively impermeable to kidney cells but not to liver cells. The high content of glucose in Collins and Euro-collins solution effectively contracts the hypothermia induced cell edema in kidneys, but not in livers. For liver preservation, in another solution, named University of Wisconsin solution, glucose was taken away and instead raffinose and lactobionate were added. These two substances are also impermeable to cell membranes both in kidneys and livers. Now 24 hour preservation of the canine liver could be obtained (Jamieson N V, Sundberg R, Lindell S, Southard J H Belzer F O: A comparison of cold storage solutions for hepatic preservation using the isolated perfused rabbit liver, Cryobiology 25:300, 1988; Jamieson N V, Sundberg R, Lindell S, Claesson K, Moen J, Vreugdenhil P K, Wight D G D, Southard J H, Belzer F O: Preservation of the canine liver for 24-48 hours using simple cold storage with UW solution. Transplantation 46:517, 1988. These references are incorporated by reference herein.). Since 1988, University of Wisconsin solution has been the organ and tissue preservation solution most used in clinical transplantation. University of Wisconsin solution is free of calcium and has an intracellular electrolyte composition. It contains raffinose and lactobionate as cell membrane impermeable molecules to counteract the cold induced cell swelling, and it contains hydroxyetylstarch to create colloid osmotic pressure.
In an article published in 1981 (Nozick J H, Farnsworth P, Montefusco C M, Parsonnet V, Ruigrok T J C, Zimmerman A N E, Autogenous vein graft thrombosis following exposure to calcium-free solutions (Calcium paradox), J. Cardiovas. Surg., 22 166, 198 1), Nozick used an extracellular solution to irrigate and rinse external jugular veins in dogs before they were autotransplanted into the femoral artery. The veins were irrigated and kept in the extracellular solution for 45 minutes before transplantation. In one group, the irrigation solution contained calcium and another was without calcium. It was concluded that it was better to irrigate the veins with extracellular solution containing calcium. However, it must be noted that this study was not an organ preservation study where cold ischemic storage for an extended period was the goal. When Starzl tried to use Ringer""s lactate which also contains calcium, he was not able to preserve canine livers for more than 2 hours. All the researchers making efforts to develop an organ preservation solution in the 80""s, i.e. at the time of the Nozick article, knew that an organ had to be preserved based on principles far different from simply using extracellular solutions containing calcium. At that time it was dogma, not at all affected by the publication of the Nozick article, that an organ preservation solution should be free of calcium so that when the sodium potassium pump stopped due to the effects of hypothermia, no extracellular calcium could diffuse into the cells causing cell destruction.
It should also be noted that Nozick et al. only performed morphological studies, i.e. electron microscopic studies of the endothel anatomy, but no functional studies of the endothel, and more precisely, no studies of endothel dependent and independent relaxation, respectively, and also of the calcium influence on contraction and relaxation of the vascular smooth muscles. Thus the morphological study by Nozick et al. can in no way be correlated to the functional study by the present inventors, and it can not be concluded from the Nozick et al. study that the function of the endothel and smooth muscles is influenced by calcium in such an advantageous manner as found by the present inventors.
Extracellular solutions such as Ringer""s lactate, Kreb""s solution and an LPD (xe2x80x9clow potassium dextranxe2x80x9d) solution, i.e. a so-called Perfadex solution, thus can preserve blood vessels for 2 hours at room temperature (20xc2x0 C.). However, of these three solutions, only the LPD solution contains a colloidosmotically active substance, viz. dextran 40, a large sugar molecule of an average molecular weight of about 40,000 daltons. The colloidal osmotic pressure is that part of the osmotic pressure exerted by a solution that is due to dissolved colloids, i.e. the so-called xe2x80x9csuction pressurexe2x80x9d that protein molecules and other bigger molecules which cannot pass the capillary membrane exert so as to retain fluid in the capillaries. This LPD solution, which will be defined in more detail below, thus has a colloidal osmotic pressure which is slightly higher than that of normal plasma. In a series of studies, other scientists have demonstrated that dextran 40 is favourable for preventing thrombosis by covering the endothelium, which means that activated white blood corpuscles cannot get stuck with their receptors and thus invade and consequently destruct the vessel. In long-term preservation of blood vessels, for instance 36 hours, Ringer""s lactate or Kreb""s solution cannot preserve the blood vessel in a sufficiently satisfactory manner. However, the Perfadex solution tested gave good preservation for 36 hours.
In the remaining clinical organ transplantation today, two organ preservation solutions are thus prevalent, i.e. the so-called University of Wisconsin solution and the Euro-Collins solution. These solutions are so-called intracellular preservation solutions, i.e. they have a high potassium content, a low sodium content, and no calcium. The purpose of this composition is that the cells should be allowed to xe2x80x9cswimxe2x80x9d in an intracellular inactive environment. The applicant""s research team has, however, after extensive studies demonstrated that in respect of blood vessels, the high potassium content of these intracellular solutions causes a violent vascular spasm. Therefore, there is no logic in using preservation solutions of intracellular electrolyte composition when storing vascular transplants.
In summary, then, it is important to appreciate the distinction between, on the one hand, an extracellular solution which is created for intravenous infusions of a dehydrated patient, and which is also used to irrigate and rinse tissues and wounds, and on the other hand, an organ and tissue preservation solution created for cold ischemic storage. As stated above, University of Wisconsin organ preservation solution is today the leading organ preservation solution used for clinical transplantation in the world. To preserve kidneys, livers and pancreas it is almost exclusively used by all transplant surgeons, and it is even more and more used in heart preservation. For lung preservation, the most used solution has been, and probably still is, Euro-collins solution. Both these solutions are calcium-free for the reasons earlier discussed. They have intracellular electrolyte compositions, cell impermeable molecules, and are buffered.
In heart surgery, a continuously increased use of so-called homotransplants, i.e. from one individual to another of the same species, has recently become common. This means that blood vessels are removed from recently deceased individuals, in most cases in institutes of forensic medicine, and after a short-term storage, these blood vessels are cryopreserved, i.e. they are stored in fluid nitrogen at low temperatures. In heart transplantations it is in many cases also possible to make use of the aortic root including the valve apparatus of the heart that are to be removed and discarded in any case. At present, this preparation is placed in a saline solution until it is being taken care of the next day to be cryopreserved.
In plastic surgery, the extent of microsurgical procedures increases, in which parts of organs, including blood vessels, are moved from one place in the body to another, i.e. autotransplantations. Also in this part of surgery, there is a need of a satisfactory preservation solution for the vascular system in the organs involved, such that when the organ is inserted, a perfect circulation of the blood can be established when the flow of blood is started.
A further problem, which has recently been discovered, is that in reperfusion of a transplanted organ or blood vessel, injuries to the cells may arise owing to detrimental free oxygen radicals within a few seconds up to some minutes after the implantation. Summing up, there is thus at present no quite satisfactory preservation solution available for organs and tissues or parts thereof from humans and animals, especially for blood vessels, which are to be transplanted or stored for some other purpose, for instance for medical studies. In these fields, there is thus a great global need of an improved preservation solution which does not have the drawbacks of existing preservation solutions and which preserve the original structures and functions of the organ, the tissue or parts thereof to a much greater extent and for a considerably longer period of time.
An object of the present invention is to eliminate the above drawbacks of existing preservation solutions for organs and tissues or parts thereof from humans and animals.
This object is achieved by an improved preservation solution of the type mentioned by way of introduction, containing calcium, nitroglycerin and at least one colloidosmotically active substance. Further features are stated in the appended claims.
The present invention also relates to a method for preserving organs and tissues or parts thereof from humans and animals in the preservation solution and to methods for preserving endothelium-dependent relaxation factor function in organs, tissues and parts thereof, preserving the contractile function in contractile tissue and maintaining the integrity of vascular endothelium.